|Publication number||US6762560 B1|
|Application number||US 10/341,138|
|Publication date||Jul 13, 2004|
|Filing date||Jan 13, 2003|
|Priority date||Jan 13, 2003|
|Also published as||US20040135711|
|Publication number||10341138, 341138, US 6762560 B1, US 6762560B1, US-B1-6762560, US6762560 B1, US6762560B1|
|Original Assignee||Nano Silicon Pte. Ltd.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (9), Referenced by (16), Classifications (5), Legal Events (10)|
|External Links: USPTO, USPTO Assignment, Espacenet|
(1) Field of the Invention
The invention generally relates to a method used in semiconductor manufacturing and, more particularly, to a serial to parallel data converter used in the fabrication of integrated circuits (ICs).
(2) Description of Prior Art
Serial to parallel data converters have numerous applications in electronics including circuitry where serial data from a disk or CDROM are converted to parallel format to be processed within a computer. As processing speeds increase and memory sizes grow, there is a need to reduce the time necessary to convert data from serial to parallel format.
Refer now to FIG. 1 showing a typical serial to parallel data converter. A plurality (n) of first D flip-flops (DFFA) 10-13 are provided. A serial data stream (DATA_IN) is applied to the input of each DFFA 10-13. A plurality (n) of phase clocks are applied to the corresponding clock input of each latch 10-13 such that CLK0 is applied to DFFA0, CLK1 is applied to DFFA1, etc. The output of each DFFA 10-13 is connected to the input of a corresponding second D flip-flop (DFFB) 15-18. CLKn−1 is connect through a delay 19 to each clock inputs of DFFB 15-18. The outputs of each DFFB 15-18 correspond to parallel data PD0 through PDn−1. The operation of the circuit of FIG. 1 is as follows. DATA_IN are applied to the plurality of DFFA (10-13). On the rising edge (for example) of each phase clock (CLK0-CLKn−1) the corresponding serial data bit is stored on the output of its respective DFFA. Once all n data bits are stored, the clock inputs of each DFFB 15-18 are simultaneously triggered and the data are then transferred to the corresponding parallel data output PD0 through PDn−1. The parallel data are then ready for use. The process is repeated and when the next n data bits are received, new parallel data appear at the output.
The problem with this circuit is that as speeds increase, the DFFs 15-18 may not be able to load properly before the next data bit is latched into DFFA0 10. Additionally, as serial data speeds increase, the processor using the parallel data may not be able to keep up with the presentation of parallel data. Thus, the serial data transfer must be stopped until the processor is ready to accept more parallel data. It is therefore necessary to find a better method to transfer serial to parallel data.
Other approaches related to improving serial to parallel data conversion circuits exist. U.S. Pat. No. 6,259,387 B1 to Fukazawa describes a serial-parallel converter, which uses a plurality of data extraction units, a delay unit and parallel registers for storing data for parallel distribution. U.S. Pat. No. 6,052,073 to Carr et al. discloses a serial-parallel converter using a shift register, a parallel latch and a controller for enabling and synchronizing the data stream. U.S. Pat. No. 5,777,567 to Murata et al. shows a serial-parallel converter using a delay line and phase locked loop (PLL) to synchronize the data. U.S. Pat. No. 5,561,423 to Morisaki describes a serial-parallel converter operating at high-speed and low power dissipation and utilizing differential flip-flops.
A principal object of the present invention is to provide a serial to parallel data conversion method utilizing a high-speed clock and high data rate application.
Another object of the present invention is to provide a serial to parallel data conversion circuit utilizing a high-speed clock and high data rate application.
A further object of the present invention is to provide a serial to parallel data conversion method that avoids the problem of setup between parallel loading of data and latching of the next serial data bit.
A still further object of the present invention is to provide a serial to parallel data conversion circuit that avoids the problem of setup between parallel loading of data and latching of the next serial data bit.
These objects are achieved using a serial to parallel data conversion method and circuit where the first serial data word is stored within a first n-bit register prior to presentation at the n-bit parallel output. The second serial data word is stored within a second n-bit register while the first serial data word stored within the first register is presented in parallel format at the output. The third serial data word is then stored within the first n-bit register while the second serial data word stored within the second register is presented at the output. Thus odd serial data words are stored within the first n-bit register while the contents of the second n-bit register are output and even serial data words are stored within the second n-bit register while the contents of the first n-bit register are output. By alternating data storage and data presentation the problem with setup time observed in prior art is eliminated.
In the accompanying drawings forming a material part of this description, there is shown:
FIG. 1 schematically illustrating a block diagram representation of a typical serial to parallel data conversion system;
FIG. 2 schematically illustrating a block diagram of the serial to parallel data conversion system of the present invention;
FIG. 3 illustrating a schematic representation of controller block of the serial to parallel data conversion system used in FIG. 2;
FIG. 4 illustrating a timing diagram for the controller clock of FIG. 3;
FIG. 5 illustrating a block diagram of the sampler block of the serial to parallel data conversion system used in FIG. 2;
FIG. 6 illustrating a schematic representation of the latcher block used in the sampler block of FIG. 5; and
FIG. 7 illustrating a schematic representation of the data selector block used in FIG. 2 of the present invention.
Refer now to FIG. 2, depicting in block diagram the serial to parallel data converter of the present invention. An n-bit converter is depicted. A controller circuit 20 is provided having inputs CLK0, CLKn/2 and LOCK. The phase locked loop (not shown) that maintains all the clocks (CLK0 through CLKn−1) generates the LOCK signal indicating that frequency lock has been achieved. The controller 20 outputs (LOCK_A and LOCK_B) are applied to the sampler circuit 22 along with the DATA_IN and clock signals (CLK0 through CLKn−1). The sampler 22 has a pair of outputs (DATAX
An overview of the operation of the present invention of FIG. 2 will now be discussed with additional details to follow. In the example, a rising clock edge is assumed to be the trigger, however those skilled in the art will realize that a falling edge could be used without changing the intent of the invention.
The sampler 22 has two n-bit registers A and B having outputs DATA0
Refer to FIG. 3 showing the circuit for the controller block 20. A first DFF 26 has the LOCK signal applied to the D input and the CLK0 signal applied to the clock (CLK) input. The output of the first DFF 26 (LOCK_A) is applied to the D input of the second DFF 28. CLKn/2 provides the clock (CLK) input of the second DFF 28. The output of the second DFF 28 is LOCK_B. Referring now to the timing diagram of FIG. 4 and the circuit of FIG. 3, the operation of the controller will now be provided. Prior to the LOCK signal going high, LOCK_A will be low on each edge of CLK0. Since LOCK_A provides the D input to the second DFF 28, whenever LOCK_A is low, LOCK_B will be low on each edge of CLKn/2. Once a phase locked loop lock condition is achieved, LOCK will go high and LOCK_A will become high on the next edge of CLK0. Thereafter LOCK_B will become high on the next edge of CLKn/2.
Refer now to FIG. 5, showing a block diagram of the sampler 22 of the present invention. A plurality of n LATCHER blocks 30-33 are provided. Each LATCHER block 30-33 has an input tied to the DATA_IN signal line. Each LATCHERX 30-33 has a corresponding CLKX applied to a CLK input. The first n/2 LATCHERs 30-31 have a control input (CTRL) with LOCK_A applied, while the remaining n/2 LATCHERs 32-33 have the control input (CTRL) connected to LOCK_B. Each LATCHERX 30-33 has a pair of outputs (DATAX
Referring now to FIG. 6, the detailed circuitry of the LATCHER block 30-33 is now discussed. A JK flip-flop (JKFF) 40 is provided. The JKFF 40 has the J input connected to the CTRL signal (either LOCK_A or LOCK_B) while the K input is tied high. The CLK input of the JKFF and a first and second DFF (46 and 48, respectively) are connected to the CLKX signal. The output of the JKFF 40 is the signal TOG that is in turn applied to the select inputs (SEL A/!B) of a first and second 2:1 multiplexer or MUX (42 and 44, respectively). The first MUX 42 is connected such that the DATA_IN (serial data) signal is applied to the B input and the output (Q) of the first DFF 46 is applied to the A input. The second MUX 44 is connected such that the DATA_IN (serial data) signal is applied to the A input and the output (Q) of the second DFF 48 is applied to the B input. The output (Q) of the first DFF 46 is DATAX
Still referring to FIG. 6, the operation of the LATCHER block 30-33 is now described. Initially the CTRL input (from either LOCK_A or LOCK_B) is low. Therefore on each edge of CLKX the output of the JKFF 40 (TOG) is reset (logic 0). This selects the B inputs from the first and second MUX 42 and 44. This applies DATA_IN to the D input of the first DFF 46 and DATAX
Refer now to FIG. 7, showing the circuitry of the data selector 24. There are a plurality, n, of 2 to 1 multiplexers (MUX) 50-53. Each MUX 50-53 has a pair of data inputs DATAX
With all of the blocks of the serial to parallel data system described, the overall operation will now be described in further detail. If the phase locked loop is not properly synchronized with the data stream, the LOCK signal and the LOCK_A and LOCK_B will be low. The individual TOG signals for each LATCHER 30-33 will be low and invalid DATA_IN and DATAX
While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention.
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|U.S. Classification||314/101, 341/100|
|Jan 13, 2003||AS||Assignment|
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